[llvm] 17eb6b6 - Revert "[Taildup] Don't tail-duplicate loop header with multiple successors as its latches"
Roman Lebedev via llvm-commits
llvm-commits at lists.llvm.org
Wed Nov 24 00:25:03 PST 2021
Reminder to *please* mention why something is being reverted...
On Wed, Nov 24, 2021 at 5:26 AM Jun Ma via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
>
>
> Author: Jun Ma
> Date: 2021-11-24T10:26:37+08:00
> New Revision: 17eb6b61de4b4d7a35680254a59118a0e3fa8dc9
>
> URL: https://github.com/llvm/llvm-project/commit/17eb6b61de4b4d7a35680254a59118a0e3fa8dc9
> DIFF: https://github.com/llvm/llvm-project/commit/17eb6b61de4b4d7a35680254a59118a0e3fa8dc9.diff
>
> LOG: Revert "[Taildup] Don't tail-duplicate loop header with multiple successors as its latches"
>
> This reverts commit 1f9fa549841a2ec55aa5a131bfaf83f0383c4713.
>
> Added:
>
>
> Modified:
> llvm/lib/CodeGen/TailDuplicator.cpp
> llvm/test/CodeGen/X86/tail-dup-multiple-latch-loop.ll
>
> Removed:
>
>
>
> ################################################################################
> diff --git a/llvm/lib/CodeGen/TailDuplicator.cpp b/llvm/lib/CodeGen/TailDuplicator.cpp
> index 943bd18c6c8b0..54fc6ee45d00d 100644
> --- a/llvm/lib/CodeGen/TailDuplicator.cpp
> +++ b/llvm/lib/CodeGen/TailDuplicator.cpp
> @@ -70,12 +70,6 @@ static cl::opt<unsigned> TailDupIndirectBranchSize(
> "end with indirect branches."), cl::init(20),
> cl::Hidden);
>
> -static cl::opt<unsigned> TailDupJmpTableLoopSize(
> - "tail-dup-jmptable-loop-size",
> - cl::desc("Maximum loop latches to consider tail duplication that are "
> - "successors of loop header."),
> - cl::init(128), cl::Hidden);
> -
> static cl::opt<bool>
> TailDupVerify("tail-dup-verify",
> cl::desc("Verify sanity of PHI instructions during taildup"),
> @@ -569,29 +563,6 @@ bool TailDuplicator::shouldTailDuplicate(bool IsSimple,
> if (TailBB.isSuccessor(&TailBB))
> return false;
>
> - // When doing tail-duplication with jumptable loops like:
> - // 1 -> 2 <-> 3 |
> - // \ <-> 4 |
> - // \ <-> 5 |
> - // \ <-> ... |
> - // \---> rest |
> - // quadratic number of edges and much more loops are added to CFG. This
> - // may cause compile time regression when jumptable is quiet large.
> - // So set the limit on jumptable cases.
> - auto isLargeJumpTableLoop = [](const MachineBasicBlock &TailBB) {
> - const SmallPtrSet<const MachineBasicBlock *, 8> Preds(TailBB.pred_begin(),
> - TailBB.pred_end());
> - // Check the basic block has large number of successors, all of them only
> - // have one successor which is the basic block itself.
> - return llvm::count_if(
> - TailBB.successors(), [&](const MachineBasicBlock *SuccBB) {
> - return Preds.count(SuccBB) && SuccBB->succ_size() == 1;
> - }) > TailDupJmpTableLoopSize;
> - };
> -
> - if (isLargeJumpTableLoop(TailBB))
> - return false;
> -
> // Set the limit on the cost to duplicate. When optimizing for size,
> // duplicate only one, because one branch instruction can be eliminated to
> // compensate for the duplication.
>
> diff --git a/llvm/test/CodeGen/X86/tail-dup-multiple-latch-loop.ll b/llvm/test/CodeGen/X86/tail-dup-multiple-latch-loop.ll
> index 25da377ec487b..2032c7244331c 100644
> --- a/llvm/test/CodeGen/X86/tail-dup-multiple-latch-loop.ll
> +++ b/llvm/test/CodeGen/X86/tail-dup-multiple-latch-loop.ll
> @@ -1,48 +1,76 @@
> ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
> -; RUN: llc < %s -tail-dup-jmptable-loop-size=5 -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
> +; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
> define i8* @large_loop_switch(i8* %p) {
> ; CHECK-LABEL: large_loop_switch:
> ; CHECK: # %bb.0: # %entry
> ; CHECK-NEXT: pushq %rbx
> ; CHECK-NEXT: .cfi_def_cfa_offset 16
> ; CHECK-NEXT: .cfi_offset %rbx, -16
> -; CHECK-NEXT: movq %rdi, %rsi
> +; CHECK-NEXT: movq %rdi, %rax
> ; CHECK-NEXT: movl $6, %ebx
> -; CHECK-NEXT: movl %ebx, %eax
> -; CHECK-NEXT: jmpq *.LJTI0_0(,%rax,8)
> +; CHECK-NEXT: movl %ebx, %ecx
> +; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
> +; CHECK-NEXT: .LBB0_1: # %for.cond.cleanup
> +; CHECK-NEXT: movl $530, %edi # imm = 0x212
> +; CHECK-NEXT: movq %rax, %rsi
> +; CHECK-NEXT: popq %rbx
> +; CHECK-NEXT: .cfi_def_cfa_offset 8
> +; CHECK-NEXT: jmp ccc at PLT # TAILCALL
> +; CHECK-NEXT: .p2align 4, 0x90
> ; CHECK-NEXT: .LBB0_2: # %sw.bb1
> +; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
> +; CHECK-NEXT: .cfi_def_cfa_offset 16
> ; CHECK-NEXT: movl $531, %edi # imm = 0x213
> -; CHECK-NEXT: .LBB0_3: # %for.body
> -; CHECK-NEXT: callq ccc at PLT
> -; CHECK-NEXT: .LBB0_4: # %for.body
> ; CHECK-NEXT: movq %rax, %rsi
> +; CHECK-NEXT: callq ccc at PLT
> ; CHECK-NEXT: decl %ebx
> -; CHECK-NEXT: movl %ebx, %eax
> -; CHECK-NEXT: jmpq *.LJTI0_0(,%rax,8)
> -; CHECK-NEXT: .LBB0_5: # %sw.bb3
> +; CHECK-NEXT: movl %ebx, %ecx
> +; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
> +; CHECK-NEXT: .p2align 4, 0x90
> +; CHECK-NEXT: .LBB0_3: # %sw.bb3
> +; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
> ; CHECK-NEXT: movl $532, %edi # imm = 0x214
> +; CHECK-NEXT: movq %rax, %rsi
> ; CHECK-NEXT: callq bbb at PLT
> -; CHECK-NEXT: jmp .LBB0_4
> -; CHECK-NEXT: .LBB0_7: # %sw.bb5
> +; CHECK-NEXT: decl %ebx
> +; CHECK-NEXT: movl %ebx, %ecx
> +; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
> +; CHECK-NEXT: .p2align 4, 0x90
> +; CHECK-NEXT: .LBB0_4: # %sw.bb5
> +; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
> ; CHECK-NEXT: movl $533, %edi # imm = 0x215
> +; CHECK-NEXT: movq %rax, %rsi
> ; CHECK-NEXT: callq bbb at PLT
> -; CHECK-NEXT: jmp .LBB0_4
> -; CHECK-NEXT: .LBB0_8: # %sw.bb7
> +; CHECK-NEXT: decl %ebx
> +; CHECK-NEXT: movl %ebx, %ecx
> +; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
> +; CHECK-NEXT: .p2align 4, 0x90
> +; CHECK-NEXT: .LBB0_5: # %sw.bb7
> +; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
> ; CHECK-NEXT: movl $535, %edi # imm = 0x217
> +; CHECK-NEXT: movq %rax, %rsi
> ; CHECK-NEXT: callq bbb at PLT
> -; CHECK-NEXT: jmp .LBB0_4
> -; CHECK-NEXT: .LBB0_9: # %sw.bb9
> +; CHECK-NEXT: decl %ebx
> +; CHECK-NEXT: movl %ebx, %ecx
> +; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
> +; CHECK-NEXT: .p2align 4, 0x90
> +; CHECK-NEXT: .LBB0_6: # %sw.bb9
> +; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
> ; CHECK-NEXT: movl $536, %edi # imm = 0x218
> -; CHECK-NEXT: jmp .LBB0_3
> -; CHECK-NEXT: .LBB0_10: # %sw.bb11
> +; CHECK-NEXT: movq %rax, %rsi
> +; CHECK-NEXT: callq ccc at PLT
> +; CHECK-NEXT: decl %ebx
> +; CHECK-NEXT: movl %ebx, %ecx
> +; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
> +; CHECK-NEXT: .p2align 4, 0x90
> +; CHECK-NEXT: .LBB0_7: # %sw.bb11
> +; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
> ; CHECK-NEXT: movl $658, %edi # imm = 0x292
> +; CHECK-NEXT: movq %rax, %rsi
> ; CHECK-NEXT: callq bbb at PLT
> -; CHECK-NEXT: jmp .LBB0_4
> -; CHECK-NEXT: .LBB0_11: # %for.cond.cleanup
> -; CHECK-NEXT: movl $530, %edi # imm = 0x212
> -; CHECK-NEXT: popq %rbx
> -; CHECK-NEXT: .cfi_def_cfa_offset 8
> -; CHECK-NEXT: jmp ccc at PLT # TAILCALL
> +; CHECK-NEXT: decl %ebx
> +; CHECK-NEXT: movl %ebx, %ecx
> +; CHECK-NEXT: jmpq *.LJTI0_0(,%rcx,8)
> entry:
> br label %for.body
>
>
>
>
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